FTIR Studies of the Primary Electron Donor, P700

Breton, Jacques

doi:10.1007/978-1-4020-4256-0_18

Cited by 9 publications

(7 citation statements)

References 40 publications

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“…For PSI, only the ET cofactors P700 and A 1 have been studied using FTIR DS. (P700 + -P700) FTIR DS have been produced using (static) photo-accumulation techniques, and several comprehensive reviews of work undertaken to understand the nature of the bands in (P700 + -P700) FTIR DS have appeared in the literature, the last being in 2006 [27]. Several works from our group [35][36][37], and others [38], have appeared since then.…”

Section: Introductionmentioning

confidence: 97%

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Vibrational spectroscopy of photosystem I

Hastings

2015

Biochimica et Biophysica Acta (BBA) - Bioenergetics

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Fourier transform infrared difference spectroscopy (FTIR DS) has been widely used to study the structural details of electron transfer cofactors (and their binding sites) in many types of photosynthetic protein complexes. This review focuses in particular on work that has been done to investigate the A₁cofactor in photosystem I photosynthetic reaction centers. A review of this subject area last appeared in 2006 [1], so only work undertaken since then will be covered here. Following light excitation of intact photosystem I particles the P700⁺A⁻(1) secondary radical pair state is formed within 100ps. This state decays within 300ns at room temperature, or 300μs at 77K. Given the short-lived nature of this state, it is not easily studied using "static" photo-accumulation FTIR difference techniques at either temperature. Time-resolved techniques are required. This article focuses on the use of time-resolved step-scan FTIR DS for the study of the P700⁺A⁻(1) state in intact photosystem I. Up until now, only our group has undertaken studies in this area. So, in this article, recent work undertaken in our lab is described, where we have used low-temperature (77K), microsecond time-resolved step-scan FTIR DS to study the P700⁺A⁻(1) state in photosystem I. In photosystem I a phylloquinone molecule occupies the A₁binding site. However, different quinones can be incorporated into the A1 binding site, and here work is described for photosystem I particles with plastoquinone-9, 2-phytyl naphthoquinone and 2-methyl naphthoquinone incorporated into the A₁binding site. Studies in which ¹⁸O isotope labeled phylloquinone has been incorporated into the A1 binding site are also discussed. To fully characterize PSI particles with different quinones incorporated into the A1 binding site nanosecond to millisecond visible absorption spectroscopy has been shown to be of considerable value, especially so when undertaken using identical samples under identical conditions to that used in time-resolved step-scan FTIR measurements. In this article the latest work that has been undertaken using both visible and infrared time resolved spectroscopies on the same sample will be described. Finally, vibrational spectroscopic data that has been obtained for phylloquinone in the A1 binding site in photosystem I is compared to corresponding data for ubiquinone in the QA binding site in purple bacterial reaction centers. This article is part of a Special Issue entitled: Vibrational spectroscopies and bioenergetic systems.

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Section: Introductionmentioning

confidence: 97%

“…It is now well established that the ET cofactors in large photosynthetic protein complexes can be studied in molecular specific detail using light-induced FTIR difference spectroscopy (DS) [23][24][25][26][27]. Much of the work to date utilizes a continuous light-source to photoaccumulate a steady-state population of radical pair states.…”

Section: Introductionmentioning

confidence: 99%

Vibrational spectroscopy of photosystem I

Hastings

2015

Biochimica et Biophysica Acta (BBA) - Bioenergetics

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“…5 Interpretations of the bands in this spectrum are based upon comparison to corresponding electrochemically generated (Chl-a + -Chl-a) and (pyroChl-a + -pyroChl-a) FTIR DS. 5,6 PyroChl-a is similar to Chl-a but lacks a 13 3 ester group (Figure 1A shows the structure and numbering scheme for Chl-a). The conclusions drawn from the electrochemistry experiments seamed clear-cut, and so they have never been tested or questioned in any way.…”

Section: Introductionmentioning

confidence: 99%

“…(P700 + −P700) FTIR difference spectra (DS) have been obtained . Interpretations of the bands in this spectrum are based upon comparison to corresponding electrochemically generated (Chl- a + −Chl- a ) and (pyroChl- a + −pyroChl- a ) FTIR DS. , PyroChl- a is similar to Chl- a but lacks a 13 3 ester group (Figure A shows the structure and numbering scheme for Chl- a ). The conclusions drawn from the electrochemistry experiments seamed clear-cut, and so they have never been tested or questioned in any way.…”

Section: Introductionmentioning

confidence: 99%

Calculation of the Vibrational Properties of Chlorophyll a in Solution

2008

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Chlorophyll a (Chl-a) is at the heart of solar energy capture and conversion in plants. Because of this, Chl-a has been the subject of innumerable studies. Recently, we have been able to use quantum mechanical methods to calculate the vibrational properties of neutral and oxidized Chl-a in the gas phase [Wang, R.; Parameswaran, S.; Hastings, G. Vib. Spectrosc. 2007, 44, 357-368]. The calculated vibrational properties do not agree with experiment, however. One factor ignored in our calculations was how solvents could impact the vibrational properties. Here we calculate the vibrational properties of Chl-a and Chl-a+ in several solvents that span a wide range of dielectric constant. The calculated and experimental (Chl-a+-Chl-a) infrared difference spectra now show a remarkable similarity. However, the composition of the calculated vibrational modes are very different from that suggested from experiment. We therefore use our calculated data to make new suggestions as to the origin of the bands in experimental (Chl-a+-Chl-a) FTIR difference spectra. We indicate why bands in experimental spectra may have been misassigned. We also point to other experimental data that support our new band assignments. Assignment of bands in (Chl-a+-Chl-a) FTIR difference spectra were first made nearly 20 years ago. These assignments have formed the basis for evaluating all "cation minus neutral" FTIR difference spectra obtained for all photosynthetic systems since then. All of these experimental FTIR difference spectra should be re-examined in light of our new assignments.

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“…EPR experiments on oriented photosynthetic membranes at low temperature suggested that 3 P700 is localized on one or more Chl(s) with their plane perpendicular to the membrane (Rutherford and Sétif 1990 ), which would correspond to P A and/or P B according to the crystal structure. Fourier transform infrared (FTIR) spectroscopy provided evidence that the 3 P700 triplet is fully localized on P A (Breton 2001 , 2006 ) while optical and magnetic resonance data on a series of PSI mutants were interpreted in terms of triplet exciton localization on P B (Krabben et al 2000 ; Witt et al 2002 , 2003 ). These FTIR and ODMR experiments were done at cryogenic temperatures.…”

Section: Introductionmentioning

confidence: 99%

Primary donor triplet states of Photosystem I and II studied by Q-band pulse ENDOR spectroscopy

et al. 2022

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The photoexcited triplet state of the “primary donors” in the two photosystems of oxygenic photosynthesis has been investigated by means of electron-nuclear double resonance (ENDOR) at Q-band (34 GHz). The data obtained represent the first set of 1H hyperfine coupling tensors of the 3P700 triplet state in PSI and expand the existing data set for 3P680. We achieved an extensive assignment of the observed electron-nuclear hyperfine coupling constants (hfcs) corresponding to the methine α-protons and the methyl group β-protons of the chlorophyll (Chl) macrocycle. The data clearly confirm that in both photosystems the primary donor triplet is located on one specific monomeric Chl at cryogenic temperature. In comparison to previous transient ENDOR and pulse ENDOR experiments at standard X-band (9–10 GHz), the pulse Q-band ENDOR spectra demonstrate both improved signal-to-noise ratio and increased resolution. The observed ENDOR spectra for 3P700 and 3P680 differ in terms of the intensity loss of lines from specific methyl group protons, which is explained by hindered methyl group rotation produced by binding site effects. Contact analysis of the methyl groups in the PSI crystal structure in combination with the ENDOR analysis of 3P700 suggests that the triplet is located on the Chl aʹ (PA) in PSI. The results also provide additional evidence for the localization of 3P680 on the accessory ChlD1 in PSII.

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FTIR Studies of the Primary Electron Donor, P700

Cited by 9 publications

References 40 publications

Vibrational spectroscopy of photosystem I

Vibrational spectroscopy of photosystem I

Calculation of the Vibrational Properties of Chlorophyll a in Solution

Primary donor triplet states of Photosystem I and II studied by Q-band pulse ENDOR spectroscopy

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